Cancerous brain tumors can be “primary” tumors, meaning that the tumors originate in the brain. Primary tumors include brain tissue with mutated DNA that grows (sometimes aggressively) and displaces or replaces healthy brain tissue. Gliomas are one type of primary tumor that indicate cancer of the glial cells of the brain. While primary tumors can appear as single masses, they can often be quite large, irregularly-shaped, multi-lobed and/or infiltrated into surrounding brain tissue.
Primary tumors may not be diagnosed until the patient experiences symptoms, including those such as headaches, altered behavior, and sensory impairment. However, by the time the symptoms develop, the tumor may already be large and aggressive.
One treatment for cancerous brain tumors is surgery. Surgery involves a craniotomy (i.e., removal of a portion of the skull), dissection, and total or partial tumor resection. The objectives of surgery may include removing or lessening of the number of active malignant cells within the brain, or reducing a patient's pain or functional impairment due to the effect of the tumor on adjacent brain structures. Not only can surgery be invasive and accompanied by risks, for some tumors, surgery is often only partially effective. In other tumors, surgery may not be feasible. Surgery may risk impairment to the patient, may not be well-tolerated by the patient, and/or may involve significant costs, recovery time, and recovery efforts.
Another treatment for cancerous brain tumors is stereotactic radiosurgery (SRS). SRS is a treatment method by which multiple intersecting beams of radiation are directed at the tumor such that, at the point of intersection of the beams, a lethal dose of radiation is delivered, while tissue in the path of any single beam remains unharmed. However, confirmation that the tumor has been killed is often not possible for several months post-treatment. Furthermore, in situations where high doses of radiation may be required to kill a tumor, such as in the case of multiple or recurring tumors, it is common for the patient to reach a toxic threshold for radiation dose, prior to killing all of the tumors. Reaching this toxic threshold renders further radiation is inadvisable.